top of the lawn

urban footpath | pavement | sidewalk astronomy from Central Park, New York City

Thursday, February 26, 2009

21-hour Crescent Moon

Session name: 20090225.1730

Attempted a 21-hour crescent Moon from TotL but was clouded out on the western horizon. !! Above our heads, a deep blue sky surrounded us. With respectable altitude pearly white Venus shone brilliantly in our south southwest. Venus was spectacular in the bins, a perfectly shaped smile with that soft gradient evening terminator. Michele from the museum stopped by and shared in the observations.

Wednesday, February 25, 2009

Comet Lulin from Battery Park, NYC

Session name: 20090224.2130

This was my second observation of Comet Lulin using the Tak 22x60 binoculars. An easy starhop from Saturn to xi Leonis (Leo) 5° northwest and finalky landing on 59 Leo** abour a degree and a half west..A very pale patch light could be seen by the experienced observers about one quarter to a third of a degree northeast of 59 Leo. The comet appeared to be at least 10', maybe as large as 15' in size. I felt something central register on my eye, occurring multiple times I suspected it may have been a steliar nucleus.Unfortunately many of the others were unable to see Lulin and no wonder. Our observing party was setup directly beneath streetlamps where a blustery cold wind came off the Hudson River. Scope shake and eyepiece glare frustrated many attempts. The low surface brightness was no help. As consolation they were provided a magnificent view of Saturn and 3 moons in John's 6" scope.After the comet a few diehards, Rich R. and John S., remained to take in some of the brighter open clusters in the immense space above our heads and over New Jersey.

** 59 Leo may ring a bell, it was occulted by the Moon during the 3-4 March 2007 lunar eclipse.

Sunday, February 22, 2009

C/2007 N3, Comet Lulin observed from Central Park

Session name:20090221.2250

Eyed Comet Lulin for the first time with a pair of tripod-mounted Takahashi 22x60 binoculars from Drip Rock in Central Park. The comet appeared as a very, very faint, featureless blob, however, it had an appreciable dimension. My guess is about 15 ~ 20 minutes of arc, not quite as large as a full Moon, as judged in a 2.1° field of view (FoV). At that size it surface brightness is low resulting in very low contrast with our bright NYC background sky.

The comet was so faint doubt crept in, but repeated observations after moving off and returning to the field of view (FoV) offered the reassurance to call this a positive sighting.

The skies were mostly clear during the half hour observing session. There appeared to be some alto stratus and cirrus clouds, but nothing significant to call disruptive or obstructive. Temps were cool in the 30's (° F) with light to gentle breezes (B2 ~ B3).

The night before I conducted a short session from the same spot and scrutinized this same area. The comet was not observed since it was located nearly 7° further east along the ecliptic. I had the wrong ephemerides for that date, 20090220.2230.

Saturday afternoon at the Great Lawn

Pedestrians approach with curiosity and take in views of crescent Venus through the scope and binoculars. Tom describes why Venus is in crescent phase.

Many are astounded that Venus can be observed with the unaided eye in the day. Where do we look?

Conveniently a plane flies nearby. Serving as a "landmark", we can use this to guide people where to look. In its absence, we described Venus locations in terms of light and dark gradients in the clouds. Can you see the plane flying towards Venus in this wide field (click the image above for larger version)?

Same image as above but cropped Here's another image shortly after the plane passed Venus. Look above the contrail at an 8:45 ~ 9 o'clock direction (to the left) of the plane.

This session was cold. Long underwear, sweaters, heavy coat, hat, and gloves. When the breeze picked up the cold was biting. Awkward, sluggish movements hamper any springy, adroit dexterity. My goal was to get my first real look at Saturn this year.

The pedestrian traffic was low, yet those that stopped by were fascinated with views of Saturn and three moons. The waxing, gibbous Moon was suspended high in the southwest sky. Some of the familiar dog owners, like Mitch and Marble stopped by. When TIME'S UP! arrived for their midnight park ride, Mitch assisted by describing what and where we were observing. Marbel was occupied in chasing the ball tossed down the sidewalk. Other times, some couples passed, stopped, and chatted. Thin crowds but much company and conversation during the entire session.

Everyone marveled at Saturn and Titan under magnifications 98x and 181x. Those with keen eyes spotted Iapetus and Dione. The ring system is flat and thin, crossing the planet it appears as a very thin black line. In fact, I am not certain that I saw it entirely across the disk or if it was mostly pronounced in the center. Since Saturn hasn't reached opposition yet (08 March 2009), we should be able to see the shadow of the planet on the ring system, however, none of us picked up on this.

Screenshot from Starry Night of Saturn and attendant moons. We saw Titan, Dione, and Iapetus.

The Moon provided equal astonishment to the citizen observers. Large southern crater, Schickard straddled the terminator as it emerged from a lunar night. Just to north and west of Mare Humorum, craters Mersenius and Billy were bold enough to catch one's attention. Well formed with nice shadows, these two craters bridged the daytime time sky in the east with the morning sky in the west.

"What are you guys looking?""Is there something special today?""Is that a camera?"

These were the most frequent questions that passersby asked when Tom C. and I set up our gear at the Top of the Lawn. When we replied that one could observe the planet Venus with the unaided eye (naked eye) and also look through our optics, many accepted the offer. Our daytime astronomy session catered to a regular stream of passersby arriving in clusters of people at a time. We invited them to the eyepiece and offered to help them find the planet with the naked eye.

Unaided eyeThe crescent Moon was well above the treeline to our east in a cloudless, bluish sky. The Moon could easily been ignored if one weren't looking for her. In the daytime, a crescent moon has low contrast with the background sky, but a prompt as to where to look, one can find it without difficulty.

Looking directly south from the crescent Moon, Venus sparkled as a lonesome diamond chip. On the sky, in celestial terms, Venus was about 17° west southwest of the Moon. It was far easier describe to the public to imagine that the Moon at the center of a clock and that Venus was at a 3 o'clock position. The real difficulty was describing how far to look away from the Moon. Clouds, planes, balloons, or birds in the sky are convenient "landmarks" to direct one's attention but none were available.

Instead we used our hands to find Venus. A hand span, with pinky and thumb extended, held at arms length is about 20°. So basically recited these instructions:

Place the thumbnail beneath the Moon

Imagine the Moon is at the center of clock

Place pinky tip at the 3 o'clock position (level line)

Look above the pinky nail, this is the are of sky where to look and you can drop your hand

Relax your focus as if you are looking through and beyond the sky

When you see a small glitter, look for a star on the background sky.

Eureka!

As the day progressed, the line that Venus made with the Moon advanced to 4- and 5 o'clock orientations. I was surprised by how many spotted Venus successfully. More gratifying was when once someone spotted Venus and were eager to show others who were having trouble. Success and astonishment were breeding.

I passed around the solar paddles for those interested in looking safely at the Sun. Through the Baader solar film, one could see the entire disk of a Sun sans sunspots.

Telescope and BinocularsTom C. had the binoculars exclusively on Venus. At 16x power and observing the sunlight reflected off the cloud tops on Venus 50 million miles away, most people could make out the crescent shape of Venus.

In the telescope with a magnification of 63x, we swapped views of the Moon and Venus.

First time telescope observers were confused by what they saw in the eyepiece. They looked into the eyepiece and said they could not see Venus, all they could see was the crescent Moon. We - Tom, myself, an even observers who just left the eyepiece - told them that they were looking at Venus and no the Moon. After everyone in the crowd saw Venus, the scope was turned on the Moon for comparison and appreciation.

Everyone marveled at the size of the moon and the details of craters and mare. At this age of the moon, 5 1/2 days, Mare Necatris and the Altai Scarp were well favored to observe under the dramatic sunrise light on the Moon. This part of the Moon caught most persons attention, especially crater Theophilus with its central peak.

For those that asked if we were birding, we were not disappointed. With Tom's help we saw and identified:- a red-tailed hawk flew nearby gliding on whirlpools of air,- flocks of geese migrated between Turtle Pond and the Reservoir,- a Peregrine Falcon swooped in a circle nearby then perched on a tree to our east- and Cooper's Hawk flew across the Great Lawn.